High speed electrostatographic copying machines use different types of imaging members. Imaging members usually comprise a substrate bearing at least one organic photoconductive coating layer.
One such imaging member is the drum type. In the manufacture of drum type imaging members, at least one organic photoconductive layer is coated on a cylindrical substrate by any of a variety techniques, e.g. dip coating, spray coating, spinner coating, bead coating, wire bar coating, blade coating, roller coating, and curtain coating. It is economically advantageous to remove a defective photoconductive coating from a substrate during the manufacturing process. The ability to remove a defective or damaged photoconductive coating from a substrate without damaging the substrate so that the substrate can be recoated lowers the manufacturing costs of imaging members.
In dip coating methods, a drum substrate is vertically maintained on its axis and then successively dipped in a chemical bath containing an organic photoconductive coating material. With each successive dipping, the substrate is vertically withdrawn from the bath at a speed that will give a desired thickness for the organic photoconductive coating layer. The process is sometimes repeated to obtain a substrate drum having a plurality of organic photoconductive coating layers. These coating techniques, however, are imprecise in that the photoconductor can be contaminated by dirt or lint, or contain handling or physical defects.
In addition, after an imaging member is manufactured and has been operating in an electrostatographic copy machine or the like, it may become physically marred, or electrically fatigued such that it loses its sensitivity to light. When this happens, the imaging member must be replaced. Because substrates are among the most expensive parts of an electrostatographic copy machine to manufacture, it is economically advantageous to reclaim the substrate instead of discarding it. It is also economically advantageous to remove a photoconductive layer, and reclaim any pigment therein by chemically decomposing or dissolving the photoconductive coating layer such that the pigment can be separated from the organic binder. The pigment can then be used in a new imaging member. Ideally, it would be advantageous to remove a photoconductive layer from a substrate using environmentally compatible solvents, and immediately thereafter, rinse and recoat the substrate using one of the above coating methods to prevent recontaminating the substrate.
Various methods have been proposed for separating photoconductive coating layers from substrates. One such method is disclosed in U.S. Pat. No. 3,460,296, to C. A. Dittmar, wherein a hard coating material is removed from a relatively soft substrate by impacting the hard coating material with plastic beads having a modulus of elasticity less than the modulus of elasticity of the relatively soft substrate. This method, however, necessarily destroys the photoconductive coating layer and occasionally damages the substrate such that neither of them can be reclaimed.
Another method is disclosed in U.S. Pat. No. 4,501,621, to Abe et al., wherein a coating layer, such as a selenium coating layer, is removed from a substrate by producing cracks in the layer, introducing a volume expansive material into the cracks, and then causing the volume expansive material to expand, thereby dislodging the coating layer from the substrate. This method, however, undesirably destroys the photoconductive coating layer, and can damage the substrate sought to be reclaimed.
U.S. Pat. No. 5,085,732, to Nakamura et al., discloses a method for removing an amorphous selenium containing photoconductive layer from an electrostatographic imaging member by treating the imaging member with an aqueous solution of sodium sulfide or sodium thiourea. These solvents, however, are flammable, explodable and liberate toxic fumes.
Other methods include cutting the photoconductive coating layer from the metallic substrate; exfoliating the coating layer by repeated heating and cooling; exfoliating the coating layer by high pressure hot water ejected from a nozzle; heating the coating layer under vacuum to vaporize it; and heating the coating layer followed by chemical treatment. Each of these known methods, however, has residual problems. For example, some of the methods evolve dust or emit harmful vapors or poisonous substances. Some of these methods use environmentally incompatible solvents. And some of these methods involve heat and solvents which undesirably damage the photoconductive layer and the underlying substrate sought to be reclaimed. Directly heating an organic photoconductor also can free hazardous chemical materials including toxic fumes.